The family of a 13-year-old girl who was stabbed to death in a park by a woman with a history of mental health problems has welcomed her killer's conviction for murder.
Casey Kearney's father said his daughter's death on Valentine's Day "means we will never have the privilege of her in our lives again".
Anthony Kearney spoke after Hannah Bonser, 26, was jailed for life and told she must serve a minimum of 22 years in prison.
A jury of seven women and three men took two hours to reject Bonser's claim she was a paranoid schizophrenic who should be convicted of manslaughter due to diminished responsibility. But a judge accepted Bonser's mental health problems were a significant mitigating factor in the case.
A week-long trial at Sheffield Crown Court heard Casey was stabbed by Bonser - a total stranger with a diagnosed personality disorder and history of cannabis abuse - in Elmfield Park, Doncaster, South Yorkshire. The teenager was heading for a sleepover at a friend's house when she was stabbed once with a 16cm kitchen knife which her killer had bought earlier. Casey called 999 but only managed to say she had been stabbed. Medics fought for hours to save her but she died later that day due to severe blood loss. Her killer walked to a nearby mental health charity and handed over two knives as she confessed to what she had done.
Bonser, of Cusworth House, Doncaster, showed no emotion when the jury foreman returned the verdict or when sentence was passed. She sat in the dock looking straight ahead, as she had done throughout the week-long trial, surrounded by four prison officers.
Outside court, Mr Kearney said: "We think the jury has come to the correct decision in convicting Bonser with the murder of Casey. There was never a doubt in our minds this was a calculated and deliberate act and therefore deserves the maximum sentence our judicial system allows. However, no sentence will bring Casey back to us and the severity of Bonser's actions mean we will never have the privilege of her in our lives again."
The court heard Bonser had a long history of mental health problems and heavy cannabis use which had seen her sectioned on three separate occasions in the last decade.
Questions have now been asked about whether health professionals could have predicted she would become violent. Marjorie Wallace, chief executive of the mental health charity SANE, said: "It seems Hannah Bonser felt she was not safe in the community and begged to be sectioned in hospital, yet despite her pleas for help she was not admitted or given any consistent care. Our own experience suggests that one in three such homicides by a person with mental illness or disorder involving a stranger could have been prevented had steps been taken when warning signs emerged."
The primary healthcare trust, NHS Doncaster, said a multi-agency investigation was ongoing into the contact Bonser had with a range of services over a decade.